The regulation of tyrosine aminotransferase (TAT) synthesis by cyclic AMP (cAMP) analogs will be studied in cultured H35 hepatoma cells and rat liver. The ribosomal transit times for TAT, albumin and total soluble proteins will be measured in the presence and absence of cAMP analogs as well as dexamethasone (dex) and insulin, two other inducers of TAT. The size of TAT synthesizing polysomes plus inducers will be analyzed by one of three methods. Possible effects of cAMP analogs on the subcellular location of mRNA TAT will be examined by determining the capacity of poly A-containing fractions to direct the synthesis of TAT in a heterologous cell-free system. Attempts will be made to develop a homologous cell-free system capable of TAT synthesis where possible effects of cAMP analogs plus or minus added protein kinase can be studied. Substrates for protein kinase potentially involved in regulation of TAT synthesis will be sought; polysome-associated proteins, non-polysomal mRNP proteins as well as nascent TAT chains are ones that will be examined at first. Attempts will be made to isolate TAT-synthesizing polysomes by immunoadsorption or precipitation in order to determine whether phosphorylation of proteins actually associated with TAT synthesis is responsible for the regulation of TAT synthesis. TAT inducibility by cAMP analogs and insulin will be examined in metaphase-arrested and enucleated H35 cells. Dex is known to be ineffective in both situations. BIBLIOGRAPHIC REFERENCES: Byus, C.V., Wicks, W.D., and Russell, D.H., J. Cyclic Nucleotide Res. 2:41, 1976. Koontz, J.W., Wagner, K., Wimalasena, J., Leichtling, B.H. and Wicks, W.D., Effects of cyclic AMP derivatives on tumor cells in: Control Mechanisms In Cancer, Criss, Ono and Sabine (Eds.) Raven Press, New York, p. 169, 1976.